Electric Toothbrush And Brush Head For An Electric Toothbrush

ABSTRACT

A brush head for an electric toothbrush is disclosed. The brush head includes a plate-shaped bristle support including mounting means for the movable mounting of the bristle support, the bristle support carrying at least two outer bristle tufts and at least two inner bristle tufts, the outer bristle tufts having a greater height than the inner bristle tufts, such that in the working surface defined by the free ends of the tufts there is formed a central depression which has a groove-shaped concave bottom curved in one direction and extending substantially straight in the direction vertical thereto. At least one of the outer bristle tufts has a chamfer on its outer lying edge of its free end close to the circumferential side of the bristle support.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of International Application No. PCT/IB2009/054898, filed Nov. 4, 2009 and International Application No. PCT/IB2009/054901, filed Nov. 4, 2009, both of which claim priority to EP 08019329.5, filed Nov. 5, 2008, the substance of which is incorporated herein by reference.

FIELD OF THE INVENTION

The present disclosure relates in general to an electric toothbrush and in particular to a brush head for such an electric toothbrush, having a bristle support including mounting means for the movable mounting of the bristle support.

BACKGROUND OF THE INVENTION

On electric toothbrushes it is known to use rotationally drivable bristled sections comprising a plurality of bristle tufts which are affixed to a substantially circular, plate-shaped bristle support whose axis of rotation extends usually centrally in relation to the bristled section. The bristled section is rotated usually with an oscillating reciprocating motion, upon which an oscillating poking motion may be superimposed, where applicable.

Whereas substantially plane bristled sections, on which the free ends of the tufts lie in a common plane, were used initially, it was proposed in the interest of an improved cleaning of the interproximal spaces to use bristled sections which at the edge have longer and further protruding tufts intended to penetrate better into the interproximal areas on account of their projection. Disclosed, for example, in EP 0835081 B1 are tufts which are arranged on the circumference of a circular, rotationally drivable bristled section in the region of the longitudinal axis and project beyond the tufts arranged further inside.

Such extended tufts on the outer circumference of the bristled section have a good self-centering effect, which during rotational driving of the bristled section locates the brush centrally on the respective tooth, and really do enable an improved cleaning of the interproximal spaces, however the cleaning of the tooth flank sections adjoining the interproximal spaces fails to be optimal as yet. Furthermore, such configurations of the bristled section can no longer be moved really gently from one tooth to another, which results in the brush head producing a prodding sensation during cleaning motions in the toothbrush longitudinal direction.

Similarly constructed brush heads, which are rotationally drivable and include a central recess or depression in the working surface of the bristled section, are known from US-D 478,214, US-D 517,325 or US-D 455,556.

Also proposed in the art was a rotationally drivable toothbrush head having as a depression a curved groove which extends transversely across the bristled section, forming the bristled section's working surface and being constructed as though milled through the tufts. Through such a substantially uniaxial depression in the bristled section or its working surface it is possible to achieve not only a better holding of the dentifrice or a similar, gel-type dental cleansing agent but also a better cleaning effect on the teeth accompanied by a more agreeable, gentler cleaning sensation. The contour of the working surface, which rises to opposing circumferential sides, nestles better against the lateral tooth flanks which, so to speak, are enveloped in a snug fit so that in particular the sections of the tooth flanks adjoining the interproximal spaces are better cleaned.

However, with such known configurations of a bristled section with a groove-shaped depression extending transversely across the entire bristled section, the cleaning performance in the interproximal spaces suffers or would require excessive, undesirable contact pressures to make the central tufts bend away sufficiently. Proceeding from this realization, it is a desire to provide an improved electric toothbrush and an improved brush head therefore which prevent the disadvantages of the prior art while developing the art further in advantageous manner. In particular, it is a desire to achieve an efficient and most complete cleaning of the interproximal spaces without impairing the cleaning effect on the tooth flanks, with the brush being expected to impart a gentle, agreeable cleaning sensation during operation and afford ease of handling through a sufficient self-centering effect.

SUMMARY OF THE INVENTION

In one embodiment, a brush head for an electric toothbrush is provided. The brush head includes a bristle support and a working surface. The bristle support includes mounting means for the movable mounting of the bristle support, the bristle support carrying at least two outer bristle tufts and at least two inner bristle tufts, the outer bristle tufts having a greater height than the inner bristle tufts. The working surface being defined by the free ends of the bristles of the outer and inner bristle tufts and having a central depression which has a groove-shaped concave bottom curved in one direction. At least one of the outer bristle tufts has a chamfer on an outer lying edge of its free end close to the circumferential side of the bristle support.

In another embodiment, a brush head for an electric toothbrush is provided. The brush head includes a bristle support and a working surface. The bristle support includes mounting means for the movable mounting of the bristle support, the bristle support carrying at least two outer bristle tufts and at least two inner bristle tufts, the outer bristle tufts having a greater height than the inner bristle tufts. The working surface being defined by the free ends of the bristles of the outer and inner bristle tufts and having a central depression which has a groove-shaped concave bottom that is continuously curved in one direction. A step-shaped jump in height is provided between the central depression and the at least two outer bristle tufts.

These and other features, aspects and advantages of specific embodiments will become evident to those skilled in the art from a reading of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The embodiments set forth in the drawings are illustrative in nature and not intended to limit the invention defined by the claims. The following detailed description of the illustrative embodiments can be understood when read in conjunction with the following drawings, where like structure is indicated with like reference numerals and in which:

FIG. 1 is a schematic side view of an electric toothbrush having a rotationally drivable brush head according to an embodiment shown and illustrated herein;

FIG. 2 is a top plan view of the brush head of the toothbrush of FIG. 1;

FIG. 3 is a longitudinal sectional view of the brush head taken along the line B-B of FIG. 2 parallel to the longitudinal axis of the toothbrush;

FIG. 4 is a longitudinal sectional view of the brush head of FIG. 2 taken along the line A-A of FIG. 2;

FIG. 5 is an enlarged side view of one of the outer, longer bristle tufts of FIG. 3 in an enlarged schematic representation showing the chamfer angles of the tuft;

FIG. 6 is a schematic top plan view of the brush head of the toothbrush of FIG. 1 according to another embodiment shown and illustrated herein;

FIG. 7 is a longitudinal sectional view of the toothbrush head taken along the line B-B of FIG. 6 parallel to the longitudinal axis of the toothbrush;

FIG. 8 is a longitudinal sectional view of the brush head taken along the line A-A of FIG. 6;

FIG. 9 is a schematic top plan view of the brush head of the toothbrush of FIG. 1 according to another embodiment shown and illustrated herein;

FIG. 10 is a longitudinal sectional view of the toothbrush head taken along the line B-B of FIG. 9 parallel to the longitudinal axis of the toothbrush;

FIG. 11 is a longitudinal sectional view of the brush head taken along the line A-A of FIG. 9;

FIG. 12 is a schematic top plan view of the brush head of the toothbrush of FIG. 1 according to another embodiment shown and illustrated herein;

FIG. 13 is a longitudinal sectional view of the toothbrush head taken along the line B-B of FIG. 12 parallel to the longitudinal axis of the toothbrush;

FIG. 14 is a longitudinal sectional view of the brush head taken along the line A-A of FIG. 12;

FIG. 15 is a schematic top plan view of the brush head of the toothbrush of FIG. 1 according to another embodiment shown and illustrated herein;

FIG. 16 is a longitudinal sectional view of the toothbrush head taken along the line B-B of FIG. 15 parallel to the longitudinal axis of the toothbrush;

FIG. 17 is a longitudinal sectional view of the brush head taken along the line A-A of FIG. 15;

FIG. 18 is a schematic top plan view of the brush head of the toothbrush of FIG. 1 according to another embodiment shown and illustrated herein;

FIG. 19 is a longitudinal sectional view of the toothbrush head taken along the line B-B of FIG. 18 parallel to the longitudinal axis of the toothbrush;

FIG. 20 is a longitudinal sectional view of the brush head taken along the line A-A of FIG. 18;

FIG. 21 is a schematic top plan view of the brush head of the toothbrush of FIG. 1 according to another embodiment shown and illustrated herein;

FIG. 22 is a longitudinal sectional view of the toothbrush head taken along the line B-B of FIG. 21 parallel to the longitudinal axis of the toothbrush;

FIG. 23 is a longitudinal sectional view of the brush head taken along the line A-A of FIG. 21;

FIG. 24 is a schematic top plan view of the brush head of the toothbrush of FIG. 1 according to another embodiment shown and illustrated herein;

FIG. 25 is a longitudinal sectional view of the toothbrush head taken along the line B-B of FIG. 24 parallel to the longitudinal axis of the toothbrush;

FIG. 26 is a longitudinal sectional view of the brush head taken along the line A-A of FIG. 24;

FIG. 27 is a schematic longitudinal sectional view of the brush head of the toothbrush of FIG. 1 according to another embodiment shown and illustrated herein, in which the circumferential outer longer bristle tufts have inner chamfers on their outer ends; and

FIG. 28 is a schematic function diagram of the brush head of FIG. 27 showing how the curved working surface of the bristled section hugs a tooth flank.

DETAILED DESCRIPTION OF THE INVENTION

The following text sets forth a broad description of numerous different embodiments of the present disclosure. The description is to be construed as exemplary only and does not describe every possible embodiment since describing every possible embodiment would be impractical, if not impossible. It will be understood that any feature, characteristic, component, composition, ingredient, product, step or methodology described herein can be deleted, combined with or substituted for, in whole or part, any other feature, characteristic, component, composition, ingredient, product, step or methodology described herein. Numerous alternative embodiments could be implemented, using either current technology or technology developed after the filing date of this patent, which would still fall within the scope of the claims. All publications and patents cited herein are incorporated herein by reference.

According to the present disclosure, a detachably mountable brush head for an electric toothbrush with a bristle support that carries at least two outer bristle tufts and several inner bristle tufts is provided. In one embodiment, the free ends of the bristles of the outer and inner bristle tufts define a working surface of the brush head, i.e. the working surface is the contact surface for cleaning the teeth. The inner bristle tufts are arranged such that the free ends of the bristles of the inner bristle tufts form a central depression in the working surface, which central depression is realized as a concave groove having a curvature in one direction, which curvature is in an embodiment a continuous curvature (which means that the inner and outer bristle tufts are trimmed so as to follow the continuous curvature and thus do not approximate the continuous curvature by flat ends in a step-like manner). With continuous curvature it is meant that the trim of the bristles of each of the inner bristle tufts follows the curvature of the concave groove and hence each of the inner bristle tufts has a curved upper surface defined by the free ends of the bristles of the respective inner bristle tuft that forms a part of the working surface of the central depression. The outer bristle tufts have a greater height than the inner bristle tufts as they conclude the inner depression.

In one embodiment, the outer bristle tufts have a greater height than the inner bristle tufts at least on the side that faces the inner bristle tufts such that a step-shaped jump in height is achieved between the continuously curved central depression and the working surface formed by the outer bristle tufts. While the central depression can be formed to be optimally adapted to the surface of the teeth (i.e. the curvature of the central depression can be a compromise between the strong curvature of the molars and the low curvature of the front teeth), the step-shaped jump enables the bristles of the outer bristle tufts to deeply penetrate into the interproximal areas between the teeth. If the continuous curvature of the central depression would simply continue to the outer bristle tufts, the outer bristles of the outer bristle tufts would be trimmed with a relatively high angle (e.g. above 30 degrees with respect to a plane parallel to the bristle carrying surface of the bristle support) which renders rounding of the outer bristles as difficult. The outer bristles would most probably not get sufficiently rounded in a standard rounding process and would thus remain a sharp tip that would injure the gums in use. The bristle support has mounting means for the movable mounting of the bristle support to the brush head such that driving the bristle support into a motion, specifically a rotational oscillatory movement, by a drive arrangement of a handle section of the electric toothbrush is enabled. Overall, the proposed brush head provides very good cleaning capabilities for the frontal and lateral surfaces of the teeth and for the interproximal areas between the teeth. Further, due to the specific design, a brush head can be provided that is gentle to the gums, is self-centering and provides a smooth mouth-feel during operation.

In accordance with one embodiment, at least one of the outer bristle tufts has a chamfer on an outer lying edge of its free end close to the circumferential side of the bristle support. While the central depression with its curvature in one direction can be adapted to optimally envelope the frontal and lateral surfaces of the teeth (a compromise in the curvature can be found to accommodate both, the more strongly curved molars and the less curved front teeth), the working surface defined by the chamfer is already cleaning the lateral surface and/or (partially) the frontal surface of a neighboring tooth. Hence, while a certain tooth is cleaned by a rotational oscillating movement of the bristle support via the bristles forming the central depression, the bristle forming the chamfer already clean a part of the neighboring tooth. As the chamfer and the central depression can meet in a peak-like bristle structure, this peak-like bristle structure can penetrate into the interproximal areas for respective cleaning action.

In another embodiment, a flat plateau is formed in the working surface between the chamfer and the central depression. The bristle support has mounting means for the movable mounting of the bristle support to the brush head such that driving the bristle support into a motion, for example, a rotational oscillatory movement, by a drive arrangement of a handle section of the electric toothbrush is enabled. Overall, the proposed brush head provides very good cleaning capabilities for the frontal and lateral surfaces of the teeth and for the interproximal areas between the teeth. Further, due to the specific design, a brush head can be provided that is gentle to the gums, is self-centering and provides a smooth mouth-feel during operation. In one embodiment, the bristle support is approximately plate-shaped.

In an embodiment, the central depression has a height difference from the center of the depression to the edges of the depression of from about 0.4 mm to about 1.0 mm and in another embodiment of from about 0.6 mm to about 0.8 mm. This provides a compromise for good cleaning properties on the molars as well as on the front teeth.

In an embodiment, the angle between a tangent lying at the edge of the groove-shaped concave depression in a cross-sectional cut though the brush head and a plane lying parallel to the bristle carrying surface of the bristle support is maximally between about 10 degrees and about 25 degrees and in another embodiment between about 15 degrees and about 20 degrees. A bristle that is trimmed at such an angle below about 25 degrees and in another embodiment below about 20 degrees can sufficiently be rounded in a conventional bristle rounding procedure as is known in the art. The rounded bristles of the inner bristle tufts are thus gentle to the gums and injuries of the gums are avoided. As a result, an improved interproximal cleaning effect is achieved via the chamfer of the outer bristle tuft. In particular the lateral edges of the end surfaces can be chamfered. In one example, the outer bristle tufts can better penetrate into the interproximal spaces due to the chamfer. In another example, the brush head can be moved more easily and more gently from one tooth to the next because the chamfers of the circumferentially outer lying tufts raise the bristled section so to speak in the manner of a wedge-shaped inclined surface onto the next tooth flank. As a result, the brush head can be pushed particularly gently from one tooth to the next.

In an embodiment, the outer bristle tuft(s) can be generally chamfered towards both the inner side and the outer side, where in particular the inner chamfer concludes the central depression. As a result, the working surface of the bristled section rests with a particularly snug fit against the round-bodied tooth flanks. The inner-side chamfer is a continuation, so to speak, of the groove-shape curved depression in the center of the working surface of the bristled section. This also enhances the supra-gingival cleaning effect, that is, the cleaning of the boundary area between the hard tooth substance and the gingiva.

Depending on the application and configuration of the tufts, the chamfer can be variously pronounced. A good cleaning effect both between the teeth and on their surfaces can be achieved when said chamfer of the circumferential tufts is inclined at an angle of approximately from about 20° to about 60°, in another embodiment from about 25° to about 40°, relative to the non-chamfered end surface of said tuft. Generally, the depth of the chamfer can be variously selected, with an advantageous compromise between easy entry into the interproximal spaces and remaining cleaning capability on the tooth flanks being accomplished if said chamfer extends over approximately from about 25% to about 75% of the width of the tuft at its end. In this context, “width” is understood to mean the dimension of the tuft vertically to its longitudinal axis and transversely to the longitudinal direction of the chamfer.

Particularly effective are the outer bristle tufts, in particular in combination with the chamfers, when said tufts are inclined at least with their outer side towards the outer circumferential side at an acute angle relative to a vertical on the bristle support, at an angle in the range from about 1.5° to about 30°, in another embodiment from about 1.5° to about 15°, and in yet another embodiment from about 3° to about 5°. As a result the outer bristle tufts acquire a reduced resistance to buckling in one direction during the to and fro motion of the brush head, thus giving rise to better insertion into the interproximal spaces.

In a further aspect of the present disclosure, said outer bristle tufts have a cross-sectional area that grows larger towards their free ends and/or lateral flanks that spread apart as they progress from the bristle support. In particular said outer bristle tufts can be trapezoidally shaped as seen in a longitudinal sectional view, such that the free ends of the tuft are wider than its base on the bristle support. In one example, such a trapezoidal configuration of the tufts lends them a larger working surface on their free ends. This also enables better holding of dentifrice on the bristle ends. In another example, the fan-type spreading apart enables the bristles within a tuft to move relative to each other with greater ease, which results on the whole in a better adaptation to the tooth contour and an improved cleaning performance. In particular with lateral chamfers of the free ends of the outer bristle tufts, said tufts acquire favorable geometrical proportions with more tangible edges which nestle better against the boundary contours of the teeth.

The trapezoidal configuration of the outer bristle tufts can be asymmetric in relation to a vertical on the bristle support. In particular an inner flank of said tufts, which faces the inner bristle tufts, can extend substantially vertically to the surface of the bristle support while an outer side of the respective tuft, which faces away from the inner bristle tufts, is inclined towards the outer side at an acute angle to a vertical on the bristle support. Accordingly, the outer flanks stand off outwardly at an angle while the inner flanks stand straight, that is, they are aligned substantially vertically to the bristle support surface.

In a further embodiment, several outer bristle tufts can form with their free ends a joint, continuous surface which, seen in a plan view, can have an elongated shape. In one example, this ensures a cleaning effect covering a large area. In another example, the dentifrice or the tooth cleaning agent is held better in the inner depression of the working surface. On such an elongated bristled section, the previously mentioned chamfer on the free end of the bristled section can extend parallel and/or tangentially to the longitudinal axis of the elongated end surface.

In a further embodiment, outer bristle tufts are provided on the outer circumference in opposing circumferential sectors on opposing circumferential sides so that the central depression in the working surface of the bristled section extends between the opposing longer circumferential tufts. In this arrangement, the outer bristle tufts are not provided along the entire circumference of the bristled section but only in limited angular sectors of, for example, less than about 60° per sector angle, whereas no longer, elevated outer bristle tufts are positioned circumferentially in intermediate sectors in which the groove-shaped curved depression in the central region is at its deepest. The groove-shaped central depression extends transversely across the entire bristled section. In said sectors in which the groove-shaped depression is at its deepest, the outer circumferential tufts are adapted to the configuration of the groove-shaped depression contour or they form part of it.

The brush head can be generally driven in a variety of ways. Different drive kinematics can be implemented depending on the configuration of the toothbrush and its drive. In one embodiment, the driving motion comprises an oscillatory rotational motion about an axis of rotation which extends through the bristle support. In an embodiment, said axis of rotation can extend vertically to the plane of the bristle support through its center point or center of gravity. Optionally, an additional pulsing motion can be provided along the axis of rotation.

However, according to an alternative embodiment, it is also possible for the axis of rotation to be positioned eccentrically so that motion components of different magnitude are generated on different circumferential sides of the bristled section. In a further embodiment, the eccentricity applies to the longer, outer bristle tufts, that is, the axis of rotation is displaced parallel to a connecting line through the opposing, outer, longer tufts. Depending on the configuration of the bristled section, the eccentricity can be variously pronounced, with a good compromise between cleaning movements of desirably different size on different circumferential sides in one example and still tolerable vibrating movements and in another example being achieved when the axis of rotation divides a diameter line of the bristle support in a length ratio of from about 55% to about 45% and in another example of from about 70% to about 30%.

Alternatively or in addition, it is possible for the axis of rotation of the bristle support to be inclined at an acute angle to the plane defined by said support, with the angle of inclination being in the range from about 89° to about 65°, in another embodiment from about 88° to about 82°, relative to the plane of the bristle support. As a result it is possible, in conjunction with the groove-shaped curved surface profile of the bristled section, to superimpose a poking motion upon the rotary motion. In one embodiment, the axis of rotation is tilted such that the bristled section is tilted away from the handle section of the toothbrush.

In one embodiment, the end surface of the circumferentially outer, longer tufts, which looks elongated in the plan view, extends in an arc about the axis of rotation, in an approximately circular arc about the axis of rotation.

In another embodiment, the chamfers on the outer ends of the outer bristle tufts can nevertheless extend in a straight line, substantially tangentially to the arcuately curved, elongated end surface of the tufts. In one example, this simplifies the production of the tufts. In another example, this results in a circumferentially varying width of the chamfers and, concomitant thereto, of the non-chamfered end surfaces, which in the manner of wedge surfaces can cause the corresponding tufts to be continuously inserted into and withdrawn from the interproximal spaces.

However, according to an alternative embodiment, it is also possible for the chamfers to extend equally in an arcuate curve around the axis of rotation, in particular such that the chamfers and/or the remaining, non-chamfered end surfaces of the tufts have a contour and width that is constant in circumferential direction. As a result it is possible to achieve a particularly gentle contacting of the tufts with the tooth flanks and a favorable or uniform penetration into the interproximal spaces.

In a further embodiment, the bristle support is not of an exactly circular configuration but is of a slightly oval and/or elliptical shape. Alternatively or in addition, it is possible for at least an outer row of tufts to be arranged not on a circle but on a ring flattened on one side or on multiple sides in particular in the form of an oval and/or an ellipse. In one example, a high bristle density is achievable with a bristled section having such an oval or elliptical contour. In another example, such a form has a beneficial effect on the movement of the individual tufts. In particular when the short axis of the ellipse or the transversal axis of the oval extends parallel to the longitudinal axis of the groove-shaped contour of the central depression—which in the neutral position of the bristle support can extend in a direction transverse to the toothbrush longitudinal direction—then the outer longer tufts positioned on a diameter line arranged vertically thereto acquire an additional motion component relative to the tuft positioned in the deep region of the groove-shaped depression, so that a particularly efficient interproximal cleaning action is achieved. This elliptical or oval shape can be somewhat asymmetrically distorted from the geometrical ideal.

In one embodiment, the outer bristle tufts can enclose the inner bristle tufts along a distance covering from about 25% to about 75%, approximately, of the circumference of the bristled section or the bristle support.

In one embodiment, the inner bristle tufts, which with their free ends define said central depression in the working surface, can form with their free ends a substantially continuous surface such that a continuous concave groove-shaped depression results (here it has to differentiated between the continuous surface formed by the free ends of the bristles, which are so close together that individual bristle tufts cannot be distinguished anymore and the continuous curvature of the central depression—the latter could be achieved with a continuous surface or with a surface in which gaps between the bristle tufts are present). In one example, it is thus possible to achieve a nestling around the full surface of the tooth flanks and hence a cleaning effect covering a large area. In another example, it has a beneficial effect on the positioning of the dentifrice or the tooth cleaning agent, which is held on the working surface of the bristled section and does not flow so easily between the tufts down onto the bristle support.

The concave groove-shaped bottom, which is formed by the free ends of the bristles, can be constructed as part of a cylinder shape. In this arrangement, the radius of a section through the groove-shaped bottom or the cylinder shape is from about 9 mm to about 15 mm, in another embodiment from about 10 mm to about 13 mm and in yet another embodiment about 12 mm.

In an alternative further embodiment, said inner bristle tufts can form with their free ends separate end surfaces, as a result of which a better discharge of dislodged debris is achievable (as gaps are present between the individual free end surfaces of the bristle tufts).

In accordance with another embodiment, it is proposed to adapt the central depression with its surface contour to the curved side contour of the tooth flanks such that even without major deformations of the individual tufts the working surface of the tuft nestles against the tooth flank contour and, for interproximal cleaning, to surround the central depression with outer lying tufts which project in length or height relative to the depression. In one example, step-wise projecting tufts elevated at the circumferential edges and in another example a curved groove-shaped, contoured middle portion of the bristled section or working surface whose curvature is shaped to conform to the tooth flank contour, it is possible for the interproximal spaces to be penetrated far enough and for the lateral tooth flanks to be processed and cleaned over their full surface also in sections adjoining the interproximal spaces without excessive bending away of the middle tufts.

According to one embodiment, a step-shaped jump in height is provided between the central depression and said outer bristle tufts with the greater height. It should be noted that the bristles may also be provided in groupings other than tufts. Therefore, any reference to the tufts can also be regarded alternatively as a reference to a majority of bristles in accordance with the disclosure. Furthermore, other types of dental cleaning elements can be used alternatively instead of bristles.

Unlike bristled sections with plane depressions in the middle, the tufts in the central region and also in the areas of the bristled section oriented towards the longer, outer bristle tufts rest snugly against the lateral flanks of the teeth even without bending away. In addition, a gentler cleaning sensation results, in particular when moving the brush head from one tooth to the next, because due to the varying tuft height also in the central region individual tufts are pushed away in succession when the brush sweeps over a tooth flank, the brush head being pushed, so to speak, along the curved surface of the depression around the flank of the next tooth without the brush head falling into the depression. In particular with rotational driving of the bristled section there results in addition a gentle wiping motion because the tufts hugging the tooth flank are more intensively bent as the distance from the axis of rotation increases. The step-wise projecting outer bristle tufts give rise in addition to an intensified self-centering effect which facilitates handling.

The groove-shaped curvature of the depressed, central portion of the bristled section surface can be achieved generally in a variety of ways. For example, a correspondingly curved bristle support could be provided while the tufts are of uniform length. However, in one embodiment the tufts and in particular the inner lying tufts vary in their length such that they define with their free ends said groove-shaped curvature. In particular the length of the inner lying tufts can increase in the direction of the curvature of the working surface defined by the free ends with increasing distance from a center point of the bristle support, such as to define said groove-shaped curvature of the central depression. Through such a varying length of the tufts it is possible to achieve a gentle cleaning sensation and a gentle movement of the bristled section over the teeth because the further projecting bristles are able to bend away more easily on account of their greater length.

In one embodiment, the brush head has a groove-shaped bottom which is substantially straight or undulated in a direction vertical to the direction of the curvature. An improved adaptation of the bristle end topography in lateral tooth extension is thus provided.

In order to obtain a continuous curvature of the surface of the central depression, the free ends of the inner bristle tufts, which define said working surface in the region of the depression, do not have end surfaces extending parallel to the bristle support but end surfaces which are inclined at an acute angle to the surface of the bristle support, with different inner bristle tufts having differently inclined end surfaces, such that the differently inclined end surfaces define in mutual complementation the path of said groove-shaped contour of the central depression. In particular, the inclination of the end surfaces of the free ends of the tufts can be made increasingly more pronounced as the distance of the tufts from the center of the bristle support increases, thus resulting in an increasingly steeper wall of the groove-shaped bottom in the direction of the circumferential edges of the bristled section. In another embodiment, the free ends of the inner bristle tufts have arcuate end surfaces so as to optimally adapt to the intended continuous curvature of the central depression.

Generally the tufts may form a plane surface at their free ends. In this case the inner bristle tufts define said groove-shaped curvature in the form of a chine-type construction with a slant increasing in steps from tuft to tuft. However, in one embodiment, the free ends of the inner bristle tufts can have an end surface which is not plane but arcuate such that the mutually complementing free ends of neighboring tufts define a continuously curved enveloping surface which forms the previously mentioned groove-shaped depression. The curved end surfaces of the individual tufts are advantageously uniaxially curved, i.e., they are in themselves already curved in groove shape, so that they run in a straight line in one direction while having a curvature in a direction perpendicular thereto.

The groove-shaped curved bottom of the central region of the working surface of the bristled section can be generally of a symmetrical configuration, i.e., extending substantially parabolically. In this case the inner bristle tufts rise with their free ends at a substantially equal rate to opposing circumferential sides of the bristled section.

In another embodiment, provision can also be made for an asymmetric path of the curvature of the central depression in the working surface of the bristled section, in which case in particular a banana-shaped groove curvature can be provided. In this arrangement, the tufts defining the central depression in the working surface of the bristled section rise unequally to opposing circumferential sides so that the one upper edge of the groove-shaped depression is higher than the opposing edge. Among other things, this can be used, for example, to compensate for the tendency of users to position the brush head against the tooth flanks in a not exactly tangential but slightly V-shaped orientation. The asymmetry of the groove-shaped depression can be generally variously pronounced. In one embodiment, the asymmetric curvature can be so pronounced that an imaginary inclined plane, which sits on the highest points of the depression and/or reflects an approximately calculated mean gradient of said groove-shaped curvature, is inclined at an angle of inclination of from about 2° to about 10°, in another embodiment about 3.5°±1°, to a bristled section main axis vertical to the bristle support.

In this embodiment, the tufts arranged bilaterally on opposing sides of the central depression and projecting in height over the level of the adjoining depression sections can be of unequal height, with the difference in height lying in the range from about 5% to about 20%, in another embodiment about 10%±5%, of the height of said longer tufts and equaling in particular from about 0.3 mm to about 2 mm, and in another embodiment from about 0.5 mm to about 1.0 mm.

The asymmetric height profile with inclined working surface of the bristled section can be an advantage in particular when the bristled section with its bristled section main axis, which extends vertically onto the bristle support and/or parallel to the statistical main direction of the tufts, and/or the bristle support is/are arranged to be tilted in relation to the toothbrush axis so that the main axis of the bristled section is inclined at an acute angle to the vertical on the toothbrush longitudinal axis, in which arrangement an angle of inclination of from about 5° to about 15°, in another embodiment from about 5° to about 10°, can be provided. The inclination of the height profile of the bristled section may be orientated in opposite direction to the tilting of the bristle support so that the tilting of the bristled section is compensated for at least in part. It is thus possible, given a three-dimensional driving of the bristled section, i.e., a rotary motion about an axis of rotation and a poking motion along a poking axis which can be approximately parallel to the axis of rotation and/or to the bristled section main axis, on the one hand to reduce the intensity of the poking motion or its reaction forces on the gingiva and on the other hand to still achieve an efficient cleaning performance with retention of a self-centering effect.

A good compromise between good interproximal cleaning with sufficiently deep penetration into the interproximal spaces on the one hand and obstruction-free cleaning of the adjoining tooth flank areas and a gentle cleaning sensation on the other hand is achieved in an embodiment by the jump in height between the outer, longer tufts and the adjacent areas of the central depression being of a magnitude in the range from about 0.5 mm to about 3 mm, in another embodiment about 0.5 mm to about 1.5 mm, in another embodiment 1.5 mm±0.5 mm and in yet another embodiment from about 0.7 mm to about 0.9 mm.

In another embodiment, the bristle end topography proves to be particularly advantageous in conjunction with a rotationally oscillated brush head on which the brush head oscillates to and fro through a pivot angle. The mounting means of the bristle support hence allow for driving the bristle support in a rotational oscillatory manner via a driving arrangement present in a handle section of the electric toothbrush.

In an embodiment, the concave groove-shaped bottom of the central depression extends in a direction transverse to the longitudinal axis of the toothbrush when the bristle support is in a non-deflected neutral position. Hence, when the user holds the toothbrush in the hand during operation in a horizontal position, the concave groove-shaped depression extends vertically in this neutral position. In this holding position, the outer bristles tufts may then be arranged at the sides of the vertically extending groove (i.e. the outer bristle tufts are then arranged opposite to each other along the longitudinal axis of the toothbrush).

The exemplary electric toothbrush 1 shown in FIG. 1 comprises a handle section 2 and a brush head 4 adapted to be detachably coupled to it. The brush head 4 comprises a neck section 3 of the toothbrush 1 connected to the handle section 2, said neck section 3 being constructed in the form of a partly hollow tube. The handle section 2 accommodates in its interior an energy source 20, for example, a rechargeable battery, a motor 5, for example, an electric motor, and a control device 21.

In the embodiment shown, the rotary motion of the motor 5 is translated by means of a gearing 22 into an oscillatory rotational motion of a drive shaft 23 which extends through the neck section 3 to the distal end of the brush head 4. The toothbrush 1 can be activated and deactivated with a switch 24 mounted on the handle section 2.

In known manner using a suitable gearing (for example, a bevel gearing 25), at the end of the drive shaft 23 a bristle carrier 7 is drivable into an oscillatory rotational motion about an axis of rotation 9 which extends substantially in a direction transverse to the toothbrush longitudinal axis 26. As this occurs, the angular range swept by the bristle support 7 of the brush head 4 has a value of about ±35°±5°, with an oscillation in the range from about ±10° to about ±100° being also possible. The oscillation frequency can vary and lie, for example, between about 10 Hz and about 100 Hz. In the embodiment shown in FIG. 1, the axis of rotation 9 forms a right angle with the toothbrush longitudinal axis 26. In addition, a drive of the brush head 4 is provided in a third dimension for its pulsing motion in the direction of the axis of rotation or oscillation.

An exemplary embodiment of a brush part for use in the brush head 4 of the toothbrush 1 is shown in FIGS. 2 to 5. In this embodiment, the bristle support 7 is round, however not circular (even though a circular shape is not excluded) but slightly oval and/or elliptical, with the longer axis of the oval or the ellipse in the neutral position of the bristle support 7 extending parallel to the toothbrush longitudinal axis 26, and the shorter axis of the oval or the ellipse extending in a direction transverse to it. In FIG. 2 the longer axis of the oval or the ellipse is parallel to the line B-B.

Arranged on the bristle support 7 is a plurality of bristle tufts which are arranged in several approximately circular or non-circular rings 12, 14 and 15 and spread over the bristled section 10. Positioned on an outer ring 12 in the embodiment of FIG. 2 are eight tufts, of which four have an elongated contour while another four have a generally round or equilateral cross-sectional contour. The length of the tufts on said outer ring 12 varies, as will be explained in more detail, with generally longer tufts being provided in opposing sectors 27 and 28, which in the initial position of the bristle support 7 contain the toothbrush longitudinal axis 26, than in sectors 29 and 30, which are orientated in a direction transverse thereto or lie in between, as shown in FIG. 2.

As FIG. 2 shows, the tufts 11 and 31 lying on the outer ring 12 on the main axes B-B and A-A, respectively, are elongated in the plan view while the tufts 32 lying in between have an approximately equilateral contour or an approximately cubic or round cross-section. Said elongated tufts 11 and 31 extend in an arcuate curve around the axis of rotation 9, as shown in FIG. 2. In this arrangement, the outer bristle tufts 11 sitting on the longer main axis B-B extend over a circumferential section of from about 50° to about 90°, in another embodiment about 70°, while the outer bristle tufts 31 sitting on the shorter main axis A-A extend over a circumferential section of from about 20° to about 45°, in another embodiment about 30°.

Positioned on a second ring 15 of tufts, seen from the outside, are a total of ten tufts 13 a and 13 b, of which some have a circular cross-section and others an angular cross-section. In particular tufts 13 a with a circular cross-section are arranged, as shown in FIG. 2, in the sectors 27 and 28 in which the longer outer bristle tufts 11 of the outer ring 12 lie, while angular tufts are provided in the intermediate sectors 29 and 30 of the bristle support 7 on the second ring 14. Also, the length of these tufts 13 a and 13 b on the second ring 14 varies cyclically from tuft to tuft along the circumference of the ring 14, in such a way that longer tufts are provided in said sectors 27 and 28 than in the sectors 29 and 30 lying on the short main axis.

Finally, in an innermost region, that is, in a third ring of tufts as seen looking from the outside, two elongated tufts 13 c are provided which extend with their longitudinal dimension parallel to the longer main axis B-B.

As FIG. 3 shows, the tufts of the bristled section 10 have their free ends contoured or coordinated with each other with regard to their length and/or height, such that the working surface 34 of the bristled section 10 as defined by the free ends of the tufts has a central depression 16 with a groove-shaped bottom 17 which is curved in one direction and straight in a direction vertical to it. The curvature extends advantageously in the direction of the longer main axis B-B or in the direction of the toothbrush longitudinal axis 26 when the bristle support 7 is in its non-deflected neutral position. In a direction perpendicular thereto, which extends parallel to the shorter main axis A-A of the bristle support 7 and/or transversely to the toothbrush longitudinal axis 26 when the bristle support 7 is in its non-deflected neutral position, the depression 16 has a straight contour as shown in FIG. 4.

The central depression 16 can be constructed to be variously deep. In one embodiment, the deepest point of the depression 16 is set an amount of approximately from about 1 mm to about 3 mm, in another embodiment about 2 mm, deeper than the highest point of the bristled section 10. The groove-shaped contour of the bottom 17 of the depression 16 generally can have different curvatures. In the embodiment shown in FIGS. 3 to 5, a circular-arc-shaped contour with a curvature radius in the range from about 8 mm to about 17 mm, in another embodiment from about 10 mm to about 14 mm and in yet another embodiment about 12 mm, is provided, but this can vary depending on the dimensions and configuration of the bristled section.

As FIG. 3 shows, the end surfaces of the inner bristle tufts 13 a, 13 b and 13 c and the end surfaces of the shorter, outer bristle tufts 31, which likewise combine to define the groove-shaped bottom 17, are not constructed as plane surfaces but are likewise in themselves curved in groove shape. The groove-shaped curved end surfaces 35 complement each other and in combination form said groove-shaped contour of the bottom 17 of the central depression 16. In concrete terms, the inclination of the end surfaces of the inner bristle tufts 13 increases as the distance from the axis of rotation 9 in the direction parallel to the main axis B-B increases, as shown in FIG. 3. In other words, the tufts arranged on the transversally extending main axis A-A are slightly curved at their free ends but nevertheless are aligned substantially parallel to the bristle support surface, while the inclination of the free ends increases as the distance from said main axis A-A increases.

As FIG. 3 also shows, the outer bristle tufts 11 arranged on the outer ring 12 in sectors 27 and 28 are extended relative to the other tufts or have a greater height such that they project beyond the other tufts. This results in a step in height relative to the central depression 16, as shown in FIG. 3, that is, the central depression 16 in the embodiment shown in FIG. 3 does not merge smoothly with the end surfaces of said outer bristle tufts 11. The step may be from about 0.5 mm to about 2 mm, in another embodiment from about 0.5 mm to about 1.0 mm and in another embodiment from about 0.7 mm to about 0.9 mm.

The outer bristle tufts 11 in the opposing sectors 27 and 28, which in the neutral position of the bristle support contain the toothbrush longitudinal axis 26, have end surfaces 36 that comprise a flat section 19, which is aligned substantially vertically to the longitudinal axis of the tufts 11, as well as chamfers 18, which chamfer said end surfaces 36 towards the outside.

As FIG. 5 shows, said chamfers 18 extend at an angle γ in the range from about 20° to about 60°, in another embodiment from about 30° to about 40°. In one embodiment, the chamfers 18 are so deep and wide as to cover from about 25% to about 75% of the width W of the respective tuft 11. In this case the width W is understood to be the dimension of the tuft vertically to its longitudinal axis and vertically to the longitudinal dimension of the chamfer 18, in the region of the free end of the tuft, as shown in FIG. 5. In the embodiment shown in FIG. 5, the chamfer extends over approximately ¼ to ¾ of the width W (measured along the longitudinal axis B-B).

The longer outer bristle tufts 11 are on the whole of a trapezoidal configuration as seen in their longitudinal section. While the inner lying flank of the tuft 11 extends substantially vertically to the plane defined by the bristle support 7, the outer lying flank is inclined towards a vertical on the bristle support 7 at an angle α of from about 1.5° to about 10°, in another embodiment from about 3° to about 5°, such that the cross-section of the tuft 11 increases towards its free end, that is, the tuft becomes wider towards its free end. As a result, a large working surface is obtainable with a limited size of the bristle support 7. In addition, favorable geometrical proportions result at the free end of the tuft 11 in relation to its chamfer 18.

In order to embrace the tooth flanks as completely as possible, to distribute the brushing pressure over a wide area and to hold dentifrice or the like on the working surface 34, the tufts occupy with their free ends at least from about 35% to about 55%, in another embodiment about 50% or more of the area defined by the bristle support 7. As FIG. 2 shows, the tufts on the outer ring 12 can extend over a circumferential section of from about 200° to about 300°, when the extension of all tufts is added together. The second ring 14 of tufts, seen from the outside, can extend likewise over a circumference of from about 200° to about 300°, when the extension of all tufts along the circumference is added together. The innermost tufts can cover with their free ends advantageously an area substantially closed over its full surface.

The embodiment of the brush head 4 shown in FIGS. 6 to 8 corresponds substantially to that of FIGS. 2 to 5 so that reference is made to the corresponding preceding description in order to avoid duplicate descriptions. The embodiment of FIGS. 6 to 8 differs substantially from that of FIGS. 2 to 5 only in the somewhat deeper contour of the central, groove-shaped depression 16, which is curved with a smaller radius of curvature, and in an on the whole round contour of the non-elongated tufts 32 on the outer ring 12 of tufts.

The other embodiment of the brush head 4 of FIGS. 9 to 11 corresponds substantially to the embodiment of FIGS. 6 to 8 so that reference is made to its preceding description. Unlike said previous embodiment, the longer outer bristle tufts 11 in the sectors 27 and 28 of the bristle support 7, which in its non-deflected neutral position contain the toothbrush longitudinal axis 25, have more pronounced chamfers 18, which are chamfered at an angle γof about 55° relative to the flat sections 19 of the end surfaces 36 in order to permit an even better penetration of these tufts 11 into interproximal spaces.

In one example, some and/or all of the inner bristle tufts 13, in particular the inner bristle tufts 13 b and 13 c, which with their free ends define the groove-shaped bottom of the central depression 16, have their free ends specially constructed. Said tufts 13 b and 13 c are comprised at least partly of filaments whose ends are fanned out so that, so to speak, a soft pile and/or fleece is produced at the free ends, as a result of which dentifrice is well held particularly in this region and the tufts nestle around the tooth surface over almost its full area. The fanning out amounts to about 1.0 mm to about 2.5 mm, approximately.

The embodiment shown in FIGS. 12 to 14 corresponds substantially to the embodiment of FIGS. 9 to 11 so that reference is made to its preceding description. Unlike this preceding embodiment, the maximum difference in height between the deepest point of the depression 16 and the highest point of the bristled section is bigger and amounts to about 2 mm, approximately, for the same curvature of the bottom 17 of the depression 16. The bristles in the region of the sectors 27 and 28 differ in length. In addition, the adapting inclination between the two sides is slightly different (in the range from about 3° to about 5°). Therefore, the sectors 27 and 28 with the longer outer bristles can be either mutually similar and symmetrical or, alternatively, mutually dissimilar and asymmetrical.

The other embodiment of the brush head 4 of FIGS. 15 to 17 corresponds substantially to the preceding embodiment of FIGS. 12 to 14 so that reference is made to its preceding description. Unlike this preceding embodiment, the innermost ring 15 of the bristle support 7 includes two less greatly elongated tufts 13 c which substantially have a slightly oval cross-section and are orientated with their longitudinal axes parallel to the main axis B-B. However, as FIG. 17 shows, said innermost tufts 13 c are widened with a more pronounced taper so that their cross-section increases towards the free ends. As FIG. 17 shows, the innermost tufts 13 flare at an opening angle in the range from about 0° to about 10°, in another embodiment from about 1.5° to about 5°, such that in the region of the free ends the two tufts 13 c unite and form a joint surface while at the foot end on the bristle support 7 they are spaced from one another.

The embodiment of FIGS. 18 to 20 corresponds substantially to the preceding embodiment of FIGS. 15 to 17 so that reference is made to its preceding description. However, unlike the preceding embodiment the chamfers 18 of the elevated, outer bristle tufts 11 in the sectors 27 and 28 are of a different configuration. While the chamfers 18 of the preceding embodiments extended in a straight line, that is, in spite of the arcuate shape of the tufts 11 as seen in the plan view they defined a plane surface, the chamfers 18 of the embodiment of FIGS. 18 to 20 are arcuately curved, with the chamfers 18 being likewise curved around the axis of rotation 9 in accordance with the curved shape of the tufts 11, such that a substantially uniform chamfering of the tufts 11 results. More accurately speaking, the tufts 11 are chamfered by the same amount substantially along their entire length, that is, their dimension in the circumferential direction, because the chamfer 18 follows the shape of the tufts 11. This configuration can also be applied to all other embodiments described.

The embodiment of FIGS. 21 to 23 corresponds substantially to the embodiment of FIGS. 12 to 14 so that reference is made to its preceding description. In the embodiment of FIGS. 21 to 23, the depression 16 relative to the longer outer bristle tufts 11 is made deeper compared to FIGS. 15 to 17, such that a difference in height of 2 mm, approximately, results between the deepest point of the depression 16 and the highest point of the tufts 11.

The embodiment of FIGS. 24 to 26 corresponds substantially to the preceding embodiment of FIGS. 18 to 20 so that reference is made to its preceding description. In contrast to said preceding embodiment, the depression 16 is made deeper relative to the longer outer bristle tufts 11, such that a maximum difference in height of about 2 mm, results.

As FIG. 27 shows, the longer outer bristle tufts 11, which are arranged in the sectors 27 and 28 in which the longitudinal axis 26 of the toothbrush lies preferably in the non-deflected neutral position of the bristle support 7, can have chamfers 18 also on the inner side, that is, on the side close to the axis of rotation, and the width and angle of the chamfer 18 can correspond substantially to the previously described geometrical proportions. This applies also for the shorter outer bristles 31 of the sectors 29 and 30. As FIG. 27 shows, said tufts 11 and 31 are likewise of trapezoidal shape, with the chamfering being provided however on the inner side, that is, the inner flanks of the tufts 11 are inclined towards a vertical on the bristle support 7 at an acute angle in the range from about 1.5° to about 10° while the outer flanks stand substantially vertically to the bristle support 7.

As FIG. 28 shows, as a result of said chamfer 18 on the inner side of the longer outer bristle tufts 11 or shorter outer bristle tufts 31, the free ends of the bristles rest particularly snugly against the cambered tooth flank contour. The variant including the inner chamfer is preferred in conjunction with shorter outer bristle tufts 31 because of its ability to enhance the cleaning action on the supra-gingival tooth areas.

The dimensions and values disclosed herein are not to be understood as being strictly limited to the exact numerical values recited. Instead, unless otherwise specified, each such dimension is intended to mean both the recited value and a functionally equivalent range surrounding that value. For example, a dimension disclosed as “40 mm” is intended to mean “about 40 mm”.

Every document cited herein, including any cross referenced or related patent or application, is hereby incorporated herein by reference in its entirety unless expressly excluded or otherwise limited. The citation of any document is not an admission that it is prior art with respect to any invention disclosed or claimed herein or that it alone, or in any combination with any other reference or references, teaches, suggests or discloses any such invention. Further, to the extent that any meaning or definition of a term in this document conflicts with any meaning or definition of the same term in a document incorporated by reference, the meaning or definition assigned to that term in this document shall govern.

While particular embodiments of the present invention have been illustrated and described, it would be obvious to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the invention. It is therefore intended to cover in the appended claims all such changes and modifications that are within the scope of this invention. 

1. A brush head for an electric toothbrush, comprising: a bristle support including mounting means for the movable mounting of the bristle support, the bristle support carrying at least two outer bristle tufts and at least two inner bristle tufts, the outer bristle tufts having a greater height than the inner bristle tufts, a working surface being defined by the free ends of the bristles of the outer and inner bristle tufts and having a central depression which has a groove-shaped concave bottom curved in one direction, and wherein at least one of the outer bristle tufts has a chamfer on an outer lying edge of its free end close to the circumferential side of the bristle support.
 2. The brush head according to claim 1, wherein the curvature of the central depression is continuous.
 3. The brush head according to claim 1, wherein the mounting means are suitable to enable a rotational oscillatory movement of the bristle support.
 4. The brush head according to claim 1, wherein the chamfer is inclined relative to a flat section of the free ends of the at least two outer bristle tufts at an angle (γ) ranging between about 20° and about 60°.
 5. The brush head according to claim 1, wherein the chamfer defines a plane surface.
 6. The brush head according to claim 1, wherein the chamfer has a curvature.
 7. The brush head according to claim 1 wherein the at least two outer bristle tufts are inclined towards the circumferential side of the bristle support at an acute angle (α) in the range from about 1.5° to about 15°.
 8. The brush head according to claim 1 wherein the at least two outer bristle tufts are trapezoidally shaped as seen in a longitudinal sectional view of the at least two outer bristle tufts, with the free end of the respective outer bristle tuft being wider than its inner end.
 9. The brush head according to claim 1, wherein an inner flank of the at least two outer bristle tufts, which faces the inner bristle tufts, extends substantially vertically to the surface of the bristle support and an outer flank of the at least two outer bristle tufts is inclined towards the circumferential side of the bristle support at an acute angle to a vertical on the bristle support.
 10. The brush head according to claim 1, wherein the at least two outer bristle tufts on a first circumferential side of the bristle support are of greater height than on a second circumferential side of the bristle support.
 11. The brush head according to claim 1 wherein the mounting means of the bristle support define an axis of rotation for the bristle support suitable for producing an oscillatory rotational motion of the bristle support.
 12. The brush head according to claim 1, wherein the at least two outer bristle tufts are arranged on opposing sides of the central depression in a direction in which the groove-shaped concave bottom of the central depression has its curvature.
 13. The brush head according to claim 1 wherein the groove-shaped bottom, which is formed by the free ends of the bristles, is constructed as part of a cylinder shape.
 14. The brush head according to claim 13 wherein the radius of a section through the groove-shaped bottom or the cylinder shape is about 9 mm to about 15 mm.
 15. The brush head according to claim 1 wherein the free ends of the at least two inner bristle tufts have inclined end surfaces, with different inner bristle tufts having end surfaces with different inclinations, such as to form the groove-shaped bottom.
 16. The brush head according to claim 1 wherein the groove-shaped bottom of the central depression is shaped to raise more to one circumferential side of the bristle support than to the opposing circumferential side, exhibiting a substantially banana-shaped, asymmetric curvature.
 17. The brush head according to claim 1 wherein a step-like jump in height between the at least two outer bristle tufts and the adjacent areas of the central depression is from about 0.5 mm to about 2 mm.
 18. A brush head for an electric toothbrush, comprising: a bristle support having mounting means for the movable mounting of the bristle support, the bristle support carrying at least two outer bristle tufts and at least two inner bristle tufts, the outer bristle tufts having a greater height than the inner bristle tufts, a working surface being defined by the free ends of the bristles of the outer and inner bristle tufts and having a central depression which has a groove-shaped concave bottom that is continuously curved in one direction, and wherein a step-shaped jump in height is provided between the central depression and the at least two outer bristle tufts.
 19. The brush head according to claim 18, wherein the height of the step-shaped jump in height is between about 0.5 mm and about 2.0 mm.
 20. The brush head according to claim 18, wherein at least one of the outer bristle tufts has a chamfer at the outer lying edge of its free end. 